This invention is based on and claims priority to Japanese Patent Applications No. 2000-007572, filed Jan. 17, 2000, 2000-007574, filed Jan. 17, 2000 and No. 2000-308264, filed Oct. 6, 2000, the entire contents of which are hereby expressly incorporated by reference.
1. Field of the Invention
This invention relates to an engine for a watercraft, and particularly to an improved air induction system of an engine for a watercraft.
2. Description of Related Art
Personal watercraft have become very popular in recent years. This type of watercraft is quite sporting in nature and caries one or more riders. A relatively small hull of the personal watercraft defines a rider""s area above an engine compartment. An internal combustion engine powers a jet propulsion unit which propels the watercraft. The engine lies within the engine compartment in front of a tunnel formed on an underside of the hull. The jet propulsion unit, which includes an impeller, is placed within the tunnel. The impeller has an impeller shaft driven by the engine. The impeller shaft usually extends between the engine and the jet propulsion device through a bulkhead of the hull tunnel.
The engine includes an air induction system for introducing air into one or more combustion chambers. The air induction system includes at least one air filter associated with the combustion chambers. The air filter helps to ensure that the air entering the combustion chambers is free from foreign material. Typical air filters work well to prevent solid particulate matter from passing through the filter and into the combustion chambers, where engine damage may result. Typical air filters, however, may not be effective against liquid matter, such as water and oils. Additionally, even if the typical air filter successfully traps water within the filter, a substantial restriction of airflow may result because of the absorbed water. This reduction in airflow may adversely affect engine performance.
In addition, personal watercraft with four-cycle engines are now being produced primarily for reducing exhaust emissions. The four-cycle engine desirably includes a plenum chamber that has a relatively large volume so as to obtain high performance under all running conditions. The four-cycle engine, however, has two or more valves and a valve drive mechanism arranged to activate the valves. Such a large plenum chamber, multiple valves and a valve drive mechanism, as well as the foregoing throttle bodies, are factors which make the engine larger in height and/or width. On the other hand, because the rider""s area is defined above the engine compartment as noted above, the capacity and height of the engine compartment is limited. Otherwise, the seat position must be higher and/or wider which may not be comfortable for the rider.
Further, personal watercraft are capable of traversing relatively large distances over a body of water. As a result, the ability to perform certain routine trouble-shooting procedures in response to mechanical difficulties, while on the water, is desirable. One such routine procedure is the replacement of fouled or damaged spark plugs. However, the large plenum chambers typically utilized on personal watercraft may cover significant portions of the engine, inhibiting access to the spark plugs.
One aspect of the present invention is a filter for an induction system of a marine-duty internal combustion engine. The filter includes a water repellent element and an oil-resistant element. The water repellent element and the oil-resistant element are arranged such that air flowing through the filter passes through both the water repellent element and the oil-resistant element.
By providing the filter with a water repellent element, the filter is less likely to become clogged than known air filters for marine-duty engines. For example, some known air filters include paper or fabric filter elements which provide adequate filtration for removing foreign particles from air before passing to the combustion chamber of internal combustion engine. However, the materials commonly used for known air filters are often hydrophilic. In a marine environment, such hydrophilic elements can become swamped through contact with water vapor or droplets and thereby create undesirable restriction of airflow through the induction system. Additionally, the oil resistant element prevents oil vapor, which way travel upstream through the air induction system when the engine is not operating, from damaging other components, including the water-repellant element. Thus, by providing the filter, constructed in accordance with the present aspect of the invention, with a water repellent element, the filter prevents water absorption in the filter and the undesirable restrictions generated in known filters.
According to another aspect of the present invention, an internal combustion engine includes an engine body which defines at least one combustion chamber therein. The engine also includes an induction system configured to guide air into the combustion chamber for combustion therein. The induction system includes at least one plenum chamber having an upper portion and a lower portion, the upper and lower portions being engageable with each other, the lower portion including a removable wall.
In the art of watercraft design, and in the design of personal watercraft in particular, engine compartments are often limited in size. This limitation creates a difficulty in designing an induction system within adequately sized intake box or xe2x80x9cplenum chamberxe2x80x9d. One such difficulty arises where the air intake box interferes with access to other components within the engine compartment. Thus, by providing the plenum chamber according to be present aspect of the invention, with a removable wall disposed in a lower portion of the plan chamber, other engine components disposed behind the removable wall, can be accessed more easily.
According to a further aspect of the present invention, a marine-duty internal combustion engine includes an engine body defining at least one combustion chamber therein. The engine also includes an exhaust system for guiding exhaust gases away from the combustion chamber. Additionally, the engine includes an induction system configured to guide air along an induction airflow path to the combustion chamber for combustion therein. The induction system includes an air filter having at least a water repellent element. The engine also includes an air supply device configured to guide air from a portion of the induction system downstream from the filter into the exhaust system.
Further aspects, features and advantages of this invention will become apparent from the detailed description of the preferred embodiments which follow.